[b]1 Introduction[/b] In the metallurgical industry, wire drawing machines are crucial equipment in metal wire production. Their main function is to draw various wires into fine filaments of different specifications. Based on their working form, they are classified into straight-feed, looper, and water tank types. Among these, the straight-feed wire drawing machine represents the most advanced production technology and is also the most difficult to control electrically. It can be said that the electrical control system in straight-feed wire drawing machine production determines product quality and production efficiency. At a wire drawing machine manufacturer in Shenzhen, the electrical control system, previously provided by an engineering company in Hebei, experienced unstable tension during high-speed operation, leading to frequent wire breakage. This directly impacted the customer's equipment quality. Therefore, the manufacturer needed a more comprehensive electrical system to replace the existing one and improve its market competitiveness. The following section describes the application and effectiveness of the electrical control system, which is now composed of a Sifang E380 wire drawing machine-specific frequency converter, an LG (LS) PLC, and a WEINVIEW human-machine interface, in a straight-feed wire drawing machine. [b]2 Production Process Requirements[/b] This equipment consists of a looper, an unwinding drum, and seven drawing drums. According to the specifications of the wire to be produced, corresponding drawing dies are installed in front of each drum, decreasing in size until the last one corresponds to the required wire diameter. The wire exits the looper through the unwinding drum, passes through the first drawing die to the first drum, then from the first drum to the second drawing die, and so on, level by level, until the last one is the take-up drum. Each drum has a cylinder swing arm, used by a displacement sensor to feed tension feedback to the frequency converter. The frequency converter performs PID closed-loop control based on the feedback signal to maintain constant tension between the drums. The process requires that when changing the drawing die, the die specifications can be directly input into the human-machine interface, and the entire system can continue to operate normally after the drawing die is changed. The simplified process diagram is shown below: 3. System Control Principle In the design of the straight-line wire drawing machine, the speed ratio between each stage motor and the drum is different, with the speed ratio increasing towards the later stage. Simultaneously, the different drawing die diameters at each stage cause the wire diameter to change from large to small. However, the flow rate and volume of wire passing through the drawing die remain constant at any given moment. Therefore, changes in wire diameter also affect the speed ratio. In actual production, different wire specifications require different drawing dies, which further alters the speed ratio. In terms of logic control, the wire travels step-by-step from unwinding to drum #1 and then to the final stage of winding. During threading, drum #1 operates, and the unwinding motor and drum #1 creep. When the wire reaches drum #2, unwinding, drum #1, and drum #2 creep in tandem. This continues until the wire reaches the winding drum, at which point all preceding motors are required to creep in tandem. Each drum can also be individually jogged. Therefore, each drum needs a switch for control, including interlocking, manual, emergency stop, and foot-operated switches. The take-up drum is a self-sliding conical drum, and its diameter generally does not change during take-up. Based on this principle: The human-machine interface has logic switches for system operation and stop, alarm information (if any inverter malfunctions, the entire system stops and alerts the operator), displays the current production line speed (calculated by the PLC based on the take-up drum speed and drum diameter), and sets the aperture of each drawing die and the system operating frequency. The PLC handles all logic relationships and calculations. Using the operating frequency of the last take-up motor as a reference, the aperture of each die is obtained from the screen, and the frequency of each drum motor is calculated by combining the mechanical transmission ratio. Considering cost and the convenient communication function of the Sifang inverter, the operating frequency signals of each motor do not need to be controlled by the analog output of the D/A module; the real-time frequency is directly sent through the PLC and the inverter's 485 communication port. The inverter's operation and stop signals are controlled by the PLC outputting switch signals via external terminals. The change in the wire drawing die alters the speed ratio between each stage of the winding drum, affecting the wire tension during acceleration and deceleration. However, the Sifang frequency converter has a unique correlation between acceleration/deceleration time and linkage ratio. Therefore, during shutdown and startup, unlike other brands of frequency converters, it does not require a specific slope to accelerate or decelerate during acceleration and deceleration. In jogging and creeping, the frequency converter's jogging function is not used; instead, the running signal is used for control, avoiding wire breakage during system creeping caused by changing the wire drawing die. After the frequency and running signal are given by the PLC, the frequency converter uses the 0-10V signal fed back from the sensor for internal PID self-adjustment. The E380 series frequency converter achieves highly stable tension control through PID control with feedforward compensation. The system control diagram is as follows: [b]4 Debugging[/b] After all preparations are completed, debugging can begin. During debugging, adjust the wire drawing sequence one stage at a time, adjusting the previous stage before adjusting the next. Start with manual operation, then switch to linkage; start with low speed, then high speed. The positions of the cylinder arms and sensors will vary due to different mechanical errors. During the initial commissioning phase, the maximum and minimum values ​​of each sensor position should be calibrated. This should correspond to the maximum and minimum values ​​of the frequency converter feedback channel, which can be found in the monitoring menu "D-9". A reasonable range should have a maximum value of 100 and a minimum value of 0. Set the target value for PID control based on the sensor position; the PID will then self-adjust according to the target value. There is a pulley on the unwinding drum that can slip automatically during operation. The speed can be freely adjusted on the screen by setting a linear speed coefficient. The entire system operates based on the winding motor, so the unwinding and winding frequency converters do not require PID control and can operate in general mode. The key to the entire system commissioning lies in the settings for start-up, deceleration, shutdown, and PID control, with start-up and shutdown being particularly important during the initial commissioning phase. As can be seen from the above process diagram, the tension feedback device is installed behind the drum. Initially, when threading the wire onto each drum, perform a short-circuit adjustment before linking it to the previous stage. If the previous stage experiences wire slack, it may be due to the PID limit of that stage, requiring an appropriate increase in the PID limit (parameter F7.8). Before adjusting the winding motor, because each drum motor operates in PID mode, if the last linked motor operates in this mode, the cylinder arm will be at its maximum position due to the lack of wire behind the drum. The feedback signal will affect the current motor's speed, ultimately being limited by the PID limit. Since the linkage ratio of each stage is different, the PID limit will also vary. This may cause wire slack in the previous stage. Based on this situation, the PID limit should be gradually decreased from the previous stage to the next. After adjusting this stage's linkage, continue threading the wire, adjusting the short-circuit adjustment of the next stage, and so on, adjusting each stage sequentially until reaching the winding motor. In the linkage control mode, start low-speed operation, then stop the machine and observe the tension between each drum after shutdown. If the wire is too loose, appropriately reduce the DC braking start frequency of the associated downstream motor (parameter F4.4). If the wire is too tight, check the value of D-9 inside the inverter. This value is the tension feedback value of the displacement sensor. If the value of D-9 is greater than the PID setpoint, it is necessary to appropriately increase the DC braking start frequency of the corresponding motor. Each modification should be made in the smallest unit, increasing or decreasing, and each change should not be too large. Through repeated adjustments, it is possible to adjust it appropriately. When stopping the machine, the value of D-9 should be greater than 10 and less than the PID setpoint. According to the wire drawing machine's process, the braking start frequency should be set from small to large from the previous stage to the next stage. After stopping and adjusting, start the system at low speed. According to the production process, during system operation, the vibration of the wire is affected by the vibration of the next stage. An unreasonable PID parameter setting can easily amplify this chain reaction, which may eventually lead to the PID not keeping up and causing wire breakage. When setting PID parameters, the P value decreases from the #1 machine to the winding machine, while the I value increases from the opposite direction. The D value should be set and kept relatively unchanged. The purpose of this setting is to ensure that vibration in a later stage will inevitably affect the tension stability of the preceding stages. Vibration is then gradually reduced and eliminated through the preceding stages, ultimately maintaining the overall system tension stability. The electrical system, composed of E380 wire drawing machine-specific frequency converters, operates at a unified frequency broadcast directly from the PLC to each converter. The linkage ratio of each converter is based on the winding motor, taking into account the wire drawing die parameters and mechanical transmission ratio. This information is sent to the PLC via a panel, where it calculates and sends the linkage ratio between the machines to the EEPROM area of ​​each converter. The linkage ratio parameter is only changed when the wire drawing die is replaced. During operation, the E380 frequency converter internally adjusts the acceleration and deceleration times according to the linkage ratio to maintain constant tension and prevent wire breakage during acceleration and deceleration. The acceleration and deceleration times of each converter can be set to be the same, with acceleration ranging from 15S to 50S. The deceleration time is within 10 seconds. Because of this, it overcomes the problem of wire breakage caused by excessively short acceleration and deceleration times in general wire drawing machine systems. During the initial commissioning phase, the inverter's linkage ratio self-correction function can be activated. At low speeds, the operating frequency is directly read from the keyboard of each inverter, quickly finding the optimal linkage ratio without manual calculation, saving commissioning time. Inverter parameters should be set according to the characteristics of the on-site machinery, as some parameters may vary due to mechanical errors. The main parameter settings for each inverter are as follows: 5. Commissioning Results The electrical system of the direct-feed wire drawing machine, composed of Sifang E380 wire drawing machine-specific inverters, was successfully commissioned and the parameters optimized. The system stability was tested after mold replacement. Finally, the linear speed of normal production was one-third higher than the original electrical control system. During high-speed operation, the tension in key components (acceleration, PID adjustment, deceleration) remained very stable. With further improvements to the machinery, such as replacing ordinary motors with variable frequency motors, the speed could be further increased. The improved electrical system has also greatly enhanced the competitiveness of our customers' products in the market.